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I'm a web developer, but I've recently had some network problems. I was working on a client server, developing a new website. It has a private server, Win 2008 R2. This server has more networks adapters and it's working as a router for 75 stations inside the building(I also have a virtual machine with active directory installed so we could manage those stations). The problem comes here.

From the outside, I can accesss the websites. All works ok.

From the stations, I can go out on the internet without any problems. BUT, if from those stations I access the site hosted on server the whole system goes down(I mean the sites can't be accessed anymore. Not even from outside the building). The only way to get it back to life is to restart the remote ruter access service(joomla based).

Firstly we were using IIS, but I've changed it to apache, hopping that it would work. No luck either.

I also want to specify that there is a DNS server that is configured corectly. I'm not so goot at networks, but I'll supply all the details you'll need. I really want to make this work.

Sorry again, I'm not a network specialist, but I know some stuff. So, do you have any ideeas?

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We'd probably need to see a list of your routes on the server to see how it's routing things. –  Bart Silverstrim Feb 10 '12 at 21:41
    
Also, anything in the system logs or the web server logs? –  Bart Silverstrim Feb 10 '12 at 21:44
    
Can the stations still access the Internet when the "system" goes down? –  wfaulk Feb 10 '12 at 23:17
    
A Joomla-based remote router access service? you're going to have to elaborate a little on that. Do you mean the Routing and Remote Access (RRAS) service? How does it relate to Joomla? Also, on what interface do the clients request the web page? on the external interface? –  Mathias R. Jessen Feb 10 '12 at 23:21
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1 Answer

To me, this sounds like something funky is going on at the arp layer. The problem as you describe it sounds like you have two possible devices that can act as the internet gateway, and by accessing your websites from inside the wrong device is getting its MAC address into the arp table. Restarting the remote router access service likely triggers a gratuitous arp that puts the correct MAC into the arp table of the server.

That's my theory for what's going wrong here. This is testable though!

Before you do any internal accesses, issue the following command from the commandline:

arp -a

This will dump the arp table for the server. The gateway IP address will be in there, note what it has for a MAC address. Then hit the site from an internal host and rerun the command. If I'm right, the MAC address for the gateway will change.

As for fixing it, I don't have enough details to provide you with one. There are a couple of confounding variables:

  • The network stack for the VM. Whatever variety of virtual machine software you're running on that server can impact this.
  • The existence of the Routing and Remote Access (RRAS) service. This is the default Windows routing service, so knowing if it is installed will be helpful.
  • Any firewalls on the server itself. Sometimes these contribute to issues.
  • Any routing and firewall capabilities on the ISP device. Assuming there is some kind of cable modem, DSL line, CPE, or other device to connect the pipe from the ISP to your server, what's on that device may provide some interference.
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